Crashes whenever a pet is around?

I've had all the other expansion packs installed for the past few days and everything has been fine. Today I got round to installing Pets, redownloded the fix, etc, etc. It loads fine. It plays fine - I played for a while with my witch guy, no problems, was able to go into CAS and create a new Sim with a dog, no problem there either. Moved her in next door to the witch.

Went to tell the witch to go and ring her bell and introduce himself straight away - as soon as I scrolled over to her house, and would have soon have the dog in the screen, it crashed and I got a "Sims 3 has stopped working" error.

So I reloaded (which wasn't fun, takes about 10 minutes to do ;_;) select the Sim with the dog again. Move her in. Try to play her household. Crashes straight away again.

It only seems to do this if I try to play anything with an animal. I don't understand why, I've followed all instructions, and I used to actually own the Pets expansion on disc up until a few months ago, and it played with absolutely no problems then, so I know my PC is fully capable of running it. I've checked through the forums and FAQs for this problem, but can't find anything about the game crashing whenever a pet is around, just general crashes - which isn't what I'm after, as it works perfectly so long as there's no animal around. I don't even know if it's when ANY animal is around - the reason I made this new Sim with a dog was because I played for about a Sim week, planning to have my witch adopt a stray, but I saw no strays at all. EVER.

If I can't fix this (and I should be able to, as I said, Pets worked perfectly before!) I'll have to uninstall this pack and just not bother. :(

Did you add in any mods or cc before this? Also, your computer may just have troubles running Pets along with all the other EPs.

Isn't there a bonus for having pets as a supernatural? Might be that causing the conflict.